Tribological behaviour under loss of LUBrication of new optimized GEARs for friction reduction in power gearboxes

Informations projet

LUBGEAR

N° de convention de subvention: 101007713

DOI

10.3030/101007713

Projet clôturé

Date de signature de la CE 3 Decembre 2020

Date de début 1 Janvier 2021

Date de fin 31 Octobre 2023

Financé au titre de

• SOCIETAL CHALLENGES - Smart, Green And Integrated Transport

Coût total

€ 1 099 946,25

Contribution de l’UE

€ 1 099 946,25

Coordonné par

FUNDACION CIDETEC
Spain

Periodic Reporting for period 2 - LUBGEAR (Tribological behaviour under loss of LUBrication of new optimized GEARs for friction reduction in power gearboxes)

Période du rapport: 2022-04-01 au 2023-10-31

Résumé du contexte et des objectifs généraux du projet

To reach the goal of CO2 emissions reduction of European aviation, it is necessary to decrease the weight of the engines and to increase their efficiency. The gearbox is a key element of aero engines and its function is crucial for transmitting the right levels of power to the different aero engine components. It is formed by moving parts and lubricants are instrumental in reducing these parts wear and, in the case of components like geared turbofans, catastrophic failures. While significant time and money are invested in developing gear designs to account for all foreseeable operating conditions, not all situations are foreseeable. Therefore, one of the challenges is to develop an optimized gear design which can resist off-design conditions (i.e. lost of lubrication situations) without additional means such as secondary or auxiliary lubrication system.
LUBGEAR aims at demonstrating gear design solutions which can withstand loss of lubrication as an off-design condition in geared turbofans without additional means (secondary/auxiliary lubrication). Those solutions combine 1) optimized gear geometry for loss of lubrication environment; and 2) surface and material combinations providing low friction. The behaviour of selected solutions will be tested by means of two test rigs at different TRL: twin-disc (TRL2) for discs and FZG efficiency gear test rig for gears (TRL3). After the tests, samples will be characterized to evaluate the friction and surface damage. The solutions aim at reducing friction losses and frictional heat, leading to reduced temperatures and risk of failure. This will support the design of gears which do not face severe damage even under loss of lubrication in off-design conditions.
From the industrial point of view thanks to the acquired knowledge and developed models and methods in the project, optimized gear designs with improved performance, with lighter and less complex lubrication solution enabling the gears to operate in off-design conditions, easier maintenance and eco-friendlier features will exit. Lighter aircrafts mean less fuel consumption and less CO2 emissions. This reduction of CO2 emissions is in line with Clean Sky (aligned with European policies, ACARE and all relevant documents), aiming at reducing the product’s environment impact, while keeping competitiveness of aeronautic industry, fulfilling as consequence the European aviation environmental objectives for 2030 of decrease 50% of CO2 emissions. Besides, the longer operability will increase maintenance intervals and better Life Cycle Assessment (LCA).

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

The focus in WP1 has been to scan the state of the art related to the project to have a clearer overview of current alternatives to improve the frictional behaviour of gears in loss of lubrication conditions. Additionally, the project specifications, that is, material systems, testing conditions, lubricant, type of lubrication supply, and discs and gears geometry, were defined. These specifications are being the basis for the experimental campaign at TRL2 and TRL3 test rigs.
In WP2, the models for prediction on contact level have been developed, as well as the procurement and adaptation of the TRL 2 test rig, by means of the installation of sample temperature measurement and different vibration sensors together with synchronized online records. Additionally, a heated oil circuit with multiple temperature measurement positions for controlling temperature and avoiding overheating, and additions for oil-off conditions and verification of complete emptying of oil-box was installed. The system to measure the lubrication gap was also procured and installed.
From the other side, the discs for the TRL2 testing campaign have been produced. And finally, pre-tests and starting reference tests to evaluate the feasible parameter combinations have been performed.
In WP3, the test matrix for the first TRL3 testing campaign has been defined. In parallel the analysis and adaptation of the selected gear geometry has been carried out using a simulation software. Moreover, the gear production has started.
Last, but not least, the Plan for Communication, Dissemination and Exploitation has been launched and the first communication actions have been performed by the consortium, together with a review of the exploitation strategy.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

Currently, at industrial application level the frictional behaviour and damage of gears in off-design conditions and, especially in loss of lubrication, is still to be understood. Therefore, the following unsolved questions are being addressed by LUBGEAR project:
- Investigation of scuffing load capacity and frictional behaviour of gears in loss of lubrication and for pitch line velocities >20 m/s.
- A calculation model for predicting scuffing load capacity and frictional behaviour of gears in loss of lubrication and for pitch line velocities >20 m/s.
- Evaluation of time-to-failure for aviation gears and new material systems in case of loss of lubrication.
- Reliable and validated gear prediction tools for passive lubrication solutions.
- Extension of contact models for material behaviour at high temperatures and shear rates.
- Linking of contact models to empirical gear design simulations to enable reduced prototype tests.
- Reduction of development cycle times for new material technologies from the physical and/or chemical proof of principle to the applicability in gears by flexible testing procedure on discs in sliding velocities >25 m/s.
Considering the main project innovations, the expected progress beyond the state of the art concerns the investigation of off-design conditions, the elaboration of design and technology solutions for off-design conditions, the validation of selected design and technology solutions for gears and a roadmap for design solutions for off-design conditions.
The project outputs are expected to have essential societal impact. More than 3.0 million people are employed in the European Aircraft and Airlines industry, thus strengthening the competitiveness of this industry and related SME’s through the development of state-of-the-art technologies is vital to Europe’s economic future:
1. Due to saves and increased efficiency mainly due to the optimized gear design and improved lubricant system.
2. Technologies and tools that will result from this Project are essential to increase the European market from the current level in the next 10 years, and they will provide opportunities for the employment of highly skilled professionals. This would contribute to solving of heavy societal problems interconnected with the high unemployment in Europe derived from the economic crisis.
3. Jobs will (primarily) be created at subcontractors and suppliers, due to additional constituents of the material used, and therefore suppliers will need to increase production.
4. The new technology has broad potential applications in many other industries (helicopters, aerospace, shipbuilding, wind-energy, eMobility, etc.) creating opportunities for further employment.

Test rigs used to study the solutions in off-design conditions

Manufactured disc for TRL2 test rig

Manufactured gear for TRL3 test rig